How often do oil spills in the Gulf happen? David Hammer continues his investigation.

Recent discoveries of illegal, unreported oil discharges and systematic dumping of chemicals from rigs and platforms have raised new fears about environmental damage in the Gulf of Mexico, more than six years after the worst oil spill in U.S. history.

Tracking of federal data by the environmental watchdog group SkyTruth shows more than 11,700 oil spills have been reported in the Gulf of Mexico since the BP oil spill ended in July 2010.

But the rate of spills also has slowed significantly, from 245 a month in 2012 to 80 in October 2016.

As a part of its series “Oil & Water,” WWL-TV is taking a fresh look at how these often-overlooked spills – and an unknown number that never get reported at all – might affect the Gulf environment.

The station aired shocking video last month from a whistleblower who recorded his supervisors on an oil rig in 2014 opening a valve on a deep sea oil pipe and brazenly letting pollutants flow into the Gulf for 90 minutes, then talking about how they could cover it up.

The evidence was used to convict the oil company, Walter Oil & Gas, of a felony. There have been several other illicit violations of the Clean Water Act prosecuted by the U.S. Attorney’s Office in New Orleans in the years since BP.

Gifford Briggs of the Louisiana Oil & Gas Association said such illegal actions are “inexcusable,” but he doubts they are widespread.

“Our employees live in coastal Louisiana and when they get off the platform, they get in their boat and they go hunting, and they go fishing, and they go into the wetlands, and that’s where they raise their families, so we are as committed to the environment as anybody is,” he said.

He also said there’s no proof that the many smaller spills since the BP disaster have had any significant impact on the environment.

“Many of the incidents that get reported are very small in nature, have very quick, immediate responses and there is no immediate impact,” Briggs said.

Confronted with SkyTruth’s findings of 10,000 oil spills in the first five years after BP, averaging an aggregate of 1 million gallons of crude in the Gulf each year, Briggs said it may sound like a lot but is actually a tiny amount, especially compared with the 20 billion gallons of crude his industry safely produces in the Gulf each year. That works out to about 20,000 gallons of oil produced for each gallon spilled.

What’s more, thousands of separate spills in different locations may have polluted the Gulf with a total of 1 million gallons of crude each year since BP, but that is 200 times less than what spewed out of BP’s well, from one location over 87 days.

Jeff Short, a former government biochemist who has studied the impact of oil spills on the marine environment for decades, is publishing a new study that finds the BP spill had a cascading negative impact down the whole Gulf food chain – an impact from which certain fish species may never recover.

But he also said there’s a big difference between a singular event like the BP spill, where an immense amount of oil and chemicals were concentrated in one area, and the far more localized and limited effects of thousands of smaller spills.

Briggs contends the impact of reported oil industry spills is comparable to that of millions of naturally occurring seeps, which send oil and gas up from fissures in the seabed, often leaving small oil slicks on the Gulf surface.

Not only have Gulf species survived well amid the seeps, a 2016 study by oceanographers at Columbia University actually found they may benefit vegetative plankton that live near them.

But Jonathan Henderson, who records oil industry pollution on his Vanishing Earth blog, said the “natural seeps” argument is an old industry canard and a false comparison.

“With all these leaks and spills, it means that the infrastructure is aging,” he said. “It means that there’s nobody really watching. There’s no entity out there day by day making sure these problems are dealt with.”

He rejects Briggs’ claim that government and industry do a good job limiting the impact of spills. In spite of several industry-financed groups stood up after the BP spill to improve response capabilities, Henderson said local government officials have been reporting a lack of absorbent boom and other tools for corralling a spill.

SkyTruth criticized the efficacy of skimmers used to clean up a 90,000-gallon Shell oil spill this spring. And Henderson said he has found the Coast Guard lacks the manpower to respond to multiple spills at once.

“I flew out to a pipeline leak down along the coast in Barataria Bay, and on my way back I spotted another leak,” he said. “I called (Coast Guard) Sector New Orleans, and what they told me is that because of this other pipeline leak that they were responding to, it would likely be at least another couple of days until they would have the capacity to get to this other leak.”

Henderson said he takes flights over the Louisiana coast about three times a month and often finds oil sheens on the water. He said he’s reported more than 100 spills to the Coast Guard in the last few years, and sometimes discovers that no oil company has reported the discharge yet, even though they are required by law to report any spill they’re aware of.

“When the companies themselves are on an honor system to report how much oil was discharged, and nobody’s going out to look at it and document that, they can get away with it,” Henderson said.

The best example might be a Taylor Energy well that’s been leaking off the tip of Plaquemines Parish for the last 12 years. Hurricane Ivan caused a mudslide at Taylor’s well in 2004 and the company and government agencies have found no way to stop the steady flow from the collapsed wellhead.

The New Orleans-based company was supposed to report the extent of the leak to the Coast Guard regularly.

But it hasn’t always done so diligently: The firm was caught reporting a 10-mile slick on a day when satellite photos showed it was actually 30 miles long.

Then, an Associated Press investigation in 2015 found the volume of oil spilled was much larger than what

Taylor had been reporting, forcing the Coast Guard to raise its estimate to 20 times the previously reported amount.

“Even when these companies do report spills, they often appear to underreport the quantity of the spills and the government doesn’t appear to question that until you get attention paid to it, like with Taylor Energy or with extreme cases like the BP disaster,” said Raleigh Hoke of Gulf Restoration Network, another group based in New Orleans that monitors pollution.

Adding to the fear for environmentalists is the rise of offshore fracking, a process that shoots chemicals into the sandy formations under the Gulf floor to ease the extraction of oil. The chemicals come back up to the rig or platform, and for years, companies have been disposing of them in the processed water they are allowed to dump overboard.

The Center for Biological Diversity, another watchdog group based in California, had to sue the federal government to force the release of information about the use of chemical “frac packs” in the Gulf of Mexico. The Interior Department still hasn’t shared all of the data, but what it’s released so far shows oil companies used fracking chemicals more than 1,200 times in more than 600 wells between 2010 and 2014.

Briggs said there’s no environmental danger from fracking and the industry is ready and willing to play by any rules to keep the Gulf environment safe.

“The overwhelming majority of what comes back is just water, but that doesn’t mean it doesn’t need to be tested and it doesn’t need to be disposed of properly,” he said.

But Center for Biological Diversity attorney Kristen Monsell said the problem is the lack of those rules from the federal government. The Environmental Protection Agency is still studying the effect of the fracking chemicals.

While it imposes limits on oil and grease in the processed water oil companies can dump overboard, the agency has yet to set any similar limits on the volume of fracking chemicals.

“The Gulf of Mexico is home to incredible biological diversity and is home to habitat for whales, for dolphins, for fish and for sea turtles, and yet the EPA is allowing these companies to dump these super-dangerous chemicals directly into those habitats,” Monsell said.

“You can’t see those fracking chemicals,” Henderson adds. “When I fly out over the Gulf, I can spot an oil sheen.

But what’s really frightening is that there’s all this other stuff that’s potentially extremely harmful to the Gulf ecosystem.”